SOUTHEASTERN NORTH CAROLINA (WECT) - We are learning more about 1,4-dioxane, a second chemical found in the Brunswick and Wilmington water supply that the Environmental Protection Agency says likely causes cancer.
Tammy Hill, a water quality analyst for the NC Department of Environmental Quality (DEQ) who focuses on 1,4-dioxane, says the chemical has been in use for "a few decades."
"It is an organic compound that is used in industrial processes," Hill explained when we asked her to describe what the chemical is. "It can either be used as an ingredient or generated as a byproduct of certain industrial processes, especially plastics and textile manufacturing or recycling. It's also in some consumer goods, cleaning products and make-up."
With dioxane levels of .35 parts per billion, experts estimate your chances of getting cancer from consuming this chemical in your drinking water are 1 in 1,000,000 if you drank two liters of tap water every day for a lifetime. By comparison, there is no currently established "safe threshold" for GenX, another emerging contaminant in the Cape Fear River.
Like GenX, 1,4-dioxane is difficult for water treatment authorities to filter out.
"Once it's dissolved in water it's hard to get it back out," Hill said. "Many other contaminants can be absorbed onto substrates to pull it out of the water, but that's much harder with dioxane. So the conventional treatment processes at wastewater and water treatment plants are not made to remove the type of contaminant. So they would have to install much higher technology and much more expensive processes in order to get it out."
Sampling the Wilmington water supply in 2015, NC State University Researcher Detlef Knappe found average levels of dioxane to be 3.8 in the raw water supply, but that number was reduced to 1.2 in the finished water supply that had been treated for customers. The ozonation process used by CFPUA helped bring the level down.
That is still about three times higher than the "safe level."
For the Brunswick Regional water system, 2015 samples taken in compliance with EPA's unregulated contaminant monitoring rule numbers show average 1,4-dioxane levels of 2.1, six times higher than the safe level.
The NC DEQ began studying dioxane in the water in 2015. They learned it was coming from the wastewater treatment plants of three municipalities upriver: Asheboro, Reidsville, and Greensboro.
The concentrations of dioxane in the water there were far greater than in the Wilmington area, and this contaminant in the water supply has been making headlines there for at least a year.
"During the first year, we did find dioxane in several locations in the Cape Fear River Basin, and department representatives met with municipalities upstream from where those concentrations were found, and during the second year of the study concentrations at almost every location dropped substantially," Hill said of the study results.
Dioxane is not produced in the wastewater treatment process. It is believed that private factories in those cities were discharging the chemical into the sewer system. Dioxane then passed through the city wastewater treatment systems into the Cape Fear River, and then into the Wilmington and Brunswick water supply.
"We know that all of the municipalities have been voluntarily working with the industries in their districts on the issue and so it would be my assumption that most of (dioxane decrease measured in the second year of the study) is due to voluntary reductions by the industries involved," Hill said.
DEQ Spokesman Bridget Munger says 1,4-dioxane, GenX, and other "emerging contaminants" remain unregulated by the EPA at this point in time. However, state regulators say they will continue to push for voluntary compliance by industrial manufacturers to reduce the discharge of toxins into public waterways.
"We are pleased that we are seeing a downward trend in the numbers and we're going to continue to work with those municipalities with the goal of seeing it drop lower," Munger said.